From: bugzilla@dpdk.org
To: dev@dpdk.org
Subject: [dpdk-dev] [Bug 385] latency calculation has potential performance issues
Date: Tue, 14 Jan 2020 18:44:13 +0000 [thread overview]
Message-ID: <bug-385-3@http.bugs.dpdk.org/> (raw)
https://bugs.dpdk.org/show_bug.cgi?id=385
Bug ID: 385
Summary: latency calculation has potential performance issues
Product: DPDK
Version: 19.11
Hardware: All
OS: All
Status: UNCONFIRMED
Severity: minor
Priority: Normal
Component: other
Assignee: dev@dpdk.org
Reporter: stephen@networkplumber.org
Target Milestone: ---
If anyone is using rte_latencystats, they are in for a big performance hit.
The code in rte_latencystats uses a receive and transmit callback for each
burst. The latency calculation is using floating point (slow) and worse yet
there is several floating point divides per packet. A floating point divide is
one of the slowest opcodes on any processor.
The code should be changed to keep track of cycles (fixed point 64 bit) and
convert the result to floating point when doing update. Or better yet only
use fixed point maths.
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